Overbased oil soluble magnesium salts of sulfonic acids are used as additives in oil based compositions, such as lubricants, greases, fuels and the like. They function as detergents and acid neutralizers, thereby reducing wear and corrosion and extending engine life.
Highly basic magnesium salts of a sulfonic acid having alkalinity values (AVs) and TBNs of from 400 to 500 or higher have been difficult to prepare in a one step operation using MgO as a magnesium source. Generally, prior art processes used water and methanol as promoters, and employed ammonia, ammonium salts, low molecular weight carboxylic acids, or salts thereof, oil soluble organic acids including naphthenic and carboxylic acids, or salts thereof, and amines or amine salts of an acid as secondary promoters or activators.
In U.S. Pat. No. 3,629,109, granted to Gergel et al, there is disclosed a multistage carbonation process for preparing an overbased magnesium sulfonate. By this process, mixtures of sulfonates and carboxylates are overbased to form highly basic colloidal dispersions containing substantial quantities of overbased carboxylates.
In U.S. Pat. No. 3,875,757, granted to Kemp and U.S. Pat. No. 4,148,740, granted to Cease et al, there is disclosed an overbased magnesium sulfonate process wherein ammonia or an ammonium compound is used as a promoter or activator. These processes required the costly removal of ammonium salts from the product and condensate streams. In U.S. Pat. No. 4,129,589, granted to Eliades et al, there is disclosed another overbased magnesium sulfonate process which uses low molecular weight carboxylic acids or salts thereof, such as acetic acid, as promoters. The magnesium carbonate dispersed by this process is of a crystalline variety and not the more highly desirable amorphous carbonate.
It has now been discovered that overbased magnesium sulfonates may be prepared in a highly efficient one step operation by using a combination of reaction promoters, that when present in extremely small quantities compared to prior art reaction promoters, results in a stable, haze free, high quality overbased magnesium sulfonate which is suitable for use in various types of oil based compositions.
It is therefore an object of the invention to provide a process for manufacturing oil soluble overbased magnesium salts of sulfonic acids having alkalinity values (AVs) and TBNs ranging from 400 to 500 or higher, and wherein the product is prepared in a one step operation of contacting the reaction mixture with an acidic gas.
It is further object of the invention to provide a reaction promoter system for use in processes for manufacturing oil soluble overbased magnesium sulfonates having AVs from 400 to 500 or higher.
It is another object of the invention to provide a process for preparing overbased magnesium sulfonates wherein overbasing of the sulfonic acid is accomplished by using a promoter system in combination with a light form of MgO.